Performance of vibration welded thermoplastic joints

Abstract

The invention provides an improved method of vibration welding of thermoplastic joints. Such welding is conducted by vibrating two fiber reinforced thermoplastic parts under pressure along their common interface to generate frictional heat to melt and fuse their surfaces together. Fibers from at least one surface penetrate both into the weld and into the other surface. As a result, the welded, fiber reinforced thermoplastic surfaces have increased tensile strength than heretofore achievable. Vibration welds of reinforced thermoplastic surfaces according to this invention achieve a maximum tensile strength as high as about 120% of a weld formed by the unreinforced surfaces of corresponding thermoplastic materials.

What is claimed is: 
     
       1. A method of attaching a first surface comprising a fiber reinforced first thermoplastic composition to a second surface comprising a second thermoplastic composition which method comprises pressing together and vibrating the first and second surfaces, thereby melting each of the first and second surfaces and fusing the first and second surfaces together to thereby form a weld between the first and second surfaces which weld comprises a blend of the first and second thermoplastic compositions and wherein fibers from the first surface penetrate both into the weld and the second surface. 
     
     
       2. The method of claim 1 wherein the second thermoplastic composition is fiber reinforced and wherein fibers from the second surface penetrate both into the weld and the first surface. 
     
     
       3. The method of claim 1 wherein each of the first and second thermoplastic compositions comprises a thermoplastic polymer selected from the group consisting of polyamides, polyesters, polycarbonates, polysulfones, polyimides, polyurethanes, polyethers, vinyl polymers, and mixtures thereof. 
     
     
       4. The method of claim 1 wherein the fiber comprises a material which does not soften at temperatures of up to about 400° C. 
     
     
       5. The method of claim 1 wherein the fiber comprises a material selected from the group consisting of glass, carbon, silicon, metals, minerals, polymers and mixtures thereof. 
     
     
       6. The method of claim 2 wherein the fiber reinforcement in the first thermoplastic composition and the fiber reinforcement in the second thermoplastic composition comprise materials which do not soften at temperatures of up to about 400° C. 
     
     
       7. The method of claim 2 wherein the fiber reinforcement in the first thermoplastic composition and the fiber reinforcement in the second thermoplastic composition comprise materials selected from the group consisting of glass, carbon, silicon, metals, minerals, polymers and mixtures is thereof. 
     
     
       8. The method of claim 1 wherein the fiber is present in the reinforced first thermoplastic composition in an amount of from about 6 to about 40 weight percent based on the weight of the first thermoplastic composition. 
     
     
       9. The method of claim 1 wherein fiber is present in both the reinforced first thermoplastic composition and the reinforced second thermoplastic composition in an amount of from about 6 to about 40 weight percent based on the weight of the respective thermoplastic composition. 
     
     
       10. The method of claim 1 wherein vibration welding is conducted at a vibration amplitude of from about 0.075 inch to about 0.15 inch at a nominal frequency of about 240 Hz. 
     
     
       11. The method of claim 1 wherein vibration welding is conducted at a pressure normal to the surfaces of from about 0.6 to about 1.5 MPa. 
     
     
       12. The method of claim 1 wherein vibration welding is conducted at a hold time of from about 2 to about 8 seconds. 
     
     
       13. The method of claim 1 wherein vibration welding is conducted at a time of oscillation of from about 2 to about 7 seconds. 
     
     
       14. The method of claim 1 wherein the weld has a thickness of from about 160 micrometers to about 400 micrometers. 
     
     
       15. The method of claim 1 wherein the second thermoplastic composition is fiber reinforced and wherein fibers from the second surface penetrate both into the weld and the first surface; wherein each of the first and second thermoplastic compositions comprises a thermoplastic polymer selected from the group consisting of polyamides, polyesters, polycarbonates, polysulfones, polyimides, polyurethanes, polyethers, vinyl polymers, and mixtures thereof; wherein the fiber reinforcement in both the first thermoplastic composition and the second thermoplastic composition comprise a material selected from the group consisting of glass, carbon, silicon, metals, minerals, polymers and mixtures thereof, wherein the fiber does not soften at temperatures of up to about 400° C.; wherein the fiber present in the reinforced first thermoplastic composition and the reinforced second thermoplastic composition is present in an amount of from about 6 to about 40 weight percent based on the weight of the respective thermoplastic compositions and wherein the weld has a thickness of from about 160 micrometers to about 400 micrometers. 
     
     
       16. The method of claim 15 wherein each of the first and second thermoplastic compositions comprise a polyamide and wherein the fibers in each of the first and second thermoplastic compositions comprise glass. 
     
     
       17. The method of claim 16 wherein vibration welding is conducted at a vibration amplitude of from about 0.075 inch to about 0.15 inch at a nominal frequency of about 240 Hz; wherein vibration welding is conducted at a pressure normal to the surfaces of from about 0.6 to about 1.5 MPa; wherein vibration welding is conducted at a hold time of from about 2 to about 8 seconds; wherein vibration welding is conducted at a time of oscillation of from about 2 to about 7 seconds. 
     
     
       18. A vibration welded article produced by a method which comprises pressing together and vibrating a first surface comprising a fiber reinforced first thermoplastic composition, and a second surface comprising a second thermoplastic composition in contact with the first surface, and thereby melting each of the first and second surfaces and fusing the first and second surfaces together to thereby form a weld between the first and second surfaces comprising a blend of the first and second thermoplastic compositions and wherein fibers from the first surface penetrate both into the weld and the second surface. 
     
     
       19. The article of claim 18 wherein the second thermoplastic composition is fiber reinforced and wherein fibers from the second surface penetrate both into the weld and the first surface. 
     
     
       20. The article of claim 18 wherein each of the first and second thermoplastic compositions comprises a thermoplastic polymer selected from the group consisting of polyamides, polyesters, polycarbonates, polysulfones, polyimides, polyurethanes, polyethers, vinyl polymers, and mixtures thereof. 
     
     
       21. The article of claim 18 wherein the fiber comprises a material which does not soften at temperatures of up to about 400° C. 
     
     
       22. The article of claim 18 wherein the fiber comprises a material selected from the group consisting of glass, carbon, silicon, metals, minerals, polymers and mixtures thereof. 
     
     
       23. The article of claim 19 wherein the fiber reinforcement in the first thermoplastic composition and the fiber reinforcement in the second thermoplastic composition comprise materials which do not soften at temperatures of up to about 400° C. 
     
     
       24. The article of claim 19 wherein the fiber reinforcement in the first thermoplastic composition and the fiber reinforcement in the second thermoplastic composition comprise materials selected from the group consisting of glass, carbon, silicon, metals, minerals, polymers and mixtures thereof. 
     
     
       25. The article of claim 18 wherein the fiber is present in the reinforced first thermoplastic composition in an amount of from about 6 to about 40 weight percent based on the weight of the first thermoplastic composition. 
     
     
       26. The article of claim 18 wherein fiber is present in both the reinforced first thermoplastic composition and the reinforced second thermoplastic composition in an amount of from about 6 to about 40 weight percent based on the weight of the first thermoplastic composition. 
     
     
       27. The article of claim 18 wherein the weld has a thickness of from about 160 micrometers to about 400 micrometers. 
     
     
       28. The article of claim 18 wherein the second thermoplastic composition isfiber reinforced and wherein fibers from the second surface penetrate both into the weld and the first surface; wherein each of the first and second thermoplastic compositions comprises a thermoplastic polymer selected from the group consisting of polyamides, polyesters, polycarbonates, polysulfones, polyimides, polyurethanes, polyethers, vinyl polymers, and mixtures thereof, wherein the fiber reinforcement in both the first thermoplastic composition and the second thermoplastic composition comprise a material selected from the group consisting of glass, carbon, silicon, metals, minerals, polymers and mixtures thereof, wherein the fiber does not soften at temperatures of up to about 400° C.; wherein the fiber present in the reinforced first thermoplastic composition and the reinforced second thermoplastic composition is present in an amount of from about 6 to about 40 weight percent based on the weight of the respective thermoplastic compositions and wherein the weld has a thickness of from about 160 micrometers to about 400 micrometers. 
     
     
       29. The article of claim 28 wherein each of the first and second thermoplastic compositions comprise a polyamide and wherein the fibers in each of the first and second thermoplastic compositions comprise glass.